1. Field of the Invention
The present invention relates to an inspection adapter board having a function capable of electrically connecting a printed board as the subject of inspection to a tester for inspecting the electric performance of the printed board, an inspection method of the printed board, and a method and apparatus for producing information for fabricating the inspection adapter board.
2. Description of the Background Art
A printed wiring board (hereinafter referred to as "printed board" merely) has a function as a substrate for supporting active elements and passive elements such as integrated circuits (ICs), large scale integrated circuits (LSIs), transistors and resistors and moreover a wiring function for achieving the necessary electrical connection among electrodes related to these elements. More specifically, in the printed board, the specific arrangement of individual electrodes is determined according to the arranged state and connected conditions of elements to be supported on the printed board, and a number of electrical networks are formed by creating the electrically connected state or insulated state among these electrodes.
In general, inspection as to electrical performance of a printed board includes two of electrical conduction checking inspection (hereinafter referred to as "conduction inspection" merely) for inspecting whether no breaking of wire occurs in a wiring network in which plural electrodes on the printed board are to be electrically connected to each other, or not, and insulation checking inspection (hereinafter referred to as "insulation inspection" merely) for inspecting whether no insulation failure occurs between any two of wiring networks independently formed on the printed board, or not. The term "wiring network" as used herein means a circuit composed of a set of electrodes, 2 or more in number, electrically connected to each other, which are formed on a printed board, and printed wirings for connecting the respective electrodes to each other, including electroconductive parts for interlayer connection such as plated through holes and vias. This circuit is generally an open circuit, but may be a closed circuit or a combination thereof in some cases.
Methods for carrying out these inspections include individually inspecting methods such as a flying probe method in which inspection probes are brought into individual contact with each of a pair of electrodes to be inspected to measure an electrical resistance between both electrodes, and besides collectively inspecting methods such as a method in which pin-like probes arranged at positions corresponding to many electrodes to be inspected are collectively brought into contact with all the electrodes to be inspected, and a method making use of an inspection adapter board composed of a printed board in which inspection electrodes each having a shape and size suitable to and at positions of corresponding to electrodes to be inspected are arranged as probes in place of the pin-like probes.
In recent years, the wiring density in a printed board has been rapidly heightened, thus leading to the shortening of a distance or pitch between wirings and moreover the miniaturization of the electrodes themselves and the heightening of the arrangement density thereof. As a result, even an inspection probe unit has been naturally required to make it possible to certainly carry out the expected inspection of a printed board to be inspected, on which extremely minute electrodes to be inspected are arranged in close vicinity to one another.
The above individually inspecting methods can meet this requirement with comparative ease. However, the inspection operation must be conducted by bringing the probes into individual contact with all of many pairs of electrodes to be inspected, so that it takes a very long time to conduct the necessary inspection, which is hence unfit for actual use.
With respect to the collectively inspecting methods on the other hand, in either case where the pin-like probes are used or where the inspection adapter board having the inspection electrodes is used, a great number of minute pin probes or inspection electrodes must be arranged in a limited narrow region with high positional accuracy in an inspection probe unit. Extremely high techniques are required to realize this arrangement, so that the fabrication of such an inspection probe unit actually requires a great deal of cost and time to an impracticable extent.
In the inspection of a print board having minute and high-density wiring patterns, it is actually impossible to carry out the intended inspection if even slight misregistration occurs between a printed board as the subject of inspection and the inspection adapter board brought into contact with the printed board, so that the result of the inspection becomes unreliable. Therefore, a technique for accurately aligning them with each other has also come to be required of such inspection at the same time.
As described above, in the field of current probe units for the inspection of printed boards, there is demand for development of a specific method for arranging minute pin-like probes or inspection electrodes at high density and with high positional accuracy in response to the density heightening and miniaturization of wiring patterns in the printed board, and a study is made along this line under the circumstances.
A specific description is given with reference to FIG. 1 illustrating inspection electrodes provided on one side of an exemplary conventional inspection adapter board, which is used as an inspection probe in the method for collectively inspecting a printed board to be inspected (hereinafter may also be referred to as "board to be inspected"), and terminal electrodes provided on the other side thereof in a state laid to overlap each other or in a through-viewed state.
Inspection electrodes 51, 51 indicated by black rectangles or circles are arranged on one side of this inspection adapter board, to which the board to be inspected is opposed, and terminal electrodes 52, 52 illustrated by white circles are arranged on lattice points at regular intervals on the other side to form grids. Further, corresponding inspection electrodes 51 and terminal electrodes 52 are electrically connected to each other by a printed wiring 53 to form respective pairs.
Each of the inspection electrodes 51 conforms, in shape, size and position, with its corresponding one of many electrodes to be inspected on the board to be inspected.
Such an inspection adapter board is installed in an inspection apparatus for printed board and used to inspect the electrical performance of the board to be inspected.
FIG. 2 illustrates an example of the inspection apparatus for printed board, and reference symbols A and B indicate an inspecting head mechanism and an inspection control mechanism, respectively.
In the inspecting head mechanism A, reference numeral 10 indicates a lower head. An inspection adapter board 12 is installed on the lower head 10, and a board 20 to be inspected is arranged on the inspection adapter board 12. More specifically, the adapter board 12, on the both sides of which connector sheets 16 and 17 composed of, for example, anisotropically electroconductive rubber sheets or the like have been separately arranged, is installed in the lower head 10, and the board 20 to be inspected is arranged thereon. In an upper head 11 over the lower head 10, an inspection adapter board 12 and connector sheets 16 and 17 are installed in a state stacked in the same manner as described above.
Reference numeral 19 indicates a drive mechanism which is driven by a control mechanism 23 controlled by a controlling computer 22 in the inspection control mechanism B, whereby the lower head 10 is pressed against the upper head 11, and so each of the inspection adapter boards 12, 12 is brought into contact under pressure with the board 20 to be inspected to achieve the electrical connection between them through the connector sheets 16, 17. At this time, the conditions of electrodes to be inspected on the board 20 to be inspected as to whether the electrodes are electrically conducted or not are sent to a tester 24 through the lower head 10 and the upper head 11, thereby carrying out the inspection.
In order to carry out the necessary inspection for the board 20 to be inspected by such an inspection apparatus, it is essential to achieve a state that the positions of the electrodes to be inspected on the board 20 accurately have conformed with the positions of their corresponding inspection electrodes on the inspection adapter board 12. In order to achieve this state, any one or more of various kinds of alignment mechanisms are generally incorporated into the inspection apparatus.
However, in the existing circumstances that electrodes on a printed board have been miniaturized and heightened in density in recent years, it has been extremely difficult to accurately align the board 20 to be inspected with the inspection adapter board 12.
In the conventional inspection adapter boards, it is necessary to provide inspection electrodes in the same number and arrangement as many electrodes to be inspected on the board to be inspected in individually correspondingly to the electrodes to be inspected. Correspondingly to this, a tester is also required to have a great inspection capacity.
With the miniaturization and the heightening of arrangement density of electrodes on a printed board to be inspected, the electrical connection between the inspection electrodes and the terminal electrodes (grids) in the inspection adapter board by wirings also comes to present extreme difficulty at present. Recently, it has been impossible to form the necessary wirings within a board unless a multilayer interconnection structure, in which one or more interlayer wirings are formed, is provided, though a sufficient wiring region has heretofore been provided by both sides alone of a board.
Printed boards practically used are generally fabricated on the premise that the same kind of boards are produced in a quantity of at least certain numbers, so that their design and fabrication may be allowed to take time and cost in their own way. However, the inspection adapter board is basically fabricated as a sole product and is hence required to produce it in the production time as short as possible and at a cost as little as possible. Accordingly, the use of the multilayer interconnection structure in the inspection adapter board correspondingly to the miniaturization and density heightening of electrodes on the board to be inspected imposes a heavy burden on the fabrication of the inspection adapter board.